1. Field of the Invention
The present invention generally relates to a method and a device for equalizing mode selection and, more particularly, to a method and a device for equalizing mode selection using two sets of sampling pulses.
2. Description of the Prior Art
Generally, parasitic impedance leading to transmission loss occurs during long distance transmission, especially in high-frequency applications. In order to compensate the loss of the signal during transmission, there is often provided an equalizer at the receiving end so as to reestablish the transmitted signal and enhance the transmission reliability.
An eye diagram associated with a digital signal output from an equalizer is often used to determine whether the equalizer is good or bad. Generally, a distorted digital output from the equalizer has non-vertical edges to the time axis and has transitions shifting from the ideal timing points. By overlaying the ideal timing points, these non-vertical edges form intervals, which are often referred to as “eyes”.
Please refer to FIG. 1, which is a diagram showing comparison between a good equalizer and a bad equalizer in response to ideal sampling pulses. The ideal sampling pulses are located right in the middle of the eyes, and bigger eyes indicate a better equalizer while smaller eyes indicate a worse equalizer.
Unfortunately, the sampling pulses are usually not located right in the middle of the eyes, which leads to mistakes in determining whether an equalizer is good or bad.